U.S. patent application number 14/975896 was filed with the patent office on 2017-06-22 for active material with expansion structure for use in lithium ion batteries.
The applicant listed for this patent is NISSAN NORTH AMERICA, INC.. Invention is credited to NILESH DALE, XIAOGUANG HAO.
Application Number | 20170179467 14/975896 |
Document ID | / |
Family ID | 59066677 |
Filed Date | 2017-06-22 |
United States Patent
Application |
20170179467 |
Kind Code |
A1 |
DALE; NILESH ; et
al. |
June 22, 2017 |
ACTIVE MATERIAL WITH EXPANSION STRUCTURE FOR USE IN LITHIUM ION
BATTERIES
Abstract
An active material layer for an electrode of a lithium ion
battery has a first active material comprising silicon-based
particles, a second active material comprising graphite and
conduits between the first active material and the second active
material, the conduits being a conductive material and providing
area for expansion of the first active material due to lithiation
while maintaining contact between the first active material and the
second active material.
Inventors: |
DALE; NILESH; (Novi, MI)
; HAO; XIAOGUANG; (Wixom, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NISSAN NORTH AMERICA, INC. |
Franklin |
TN |
US |
|
|
Family ID: |
59066677 |
Appl. No.: |
14/975896 |
Filed: |
December 21, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/625 20130101;
H01M 4/387 20130101; H01M 2220/20 20130101; H01M 4/583 20130101;
H01M 4/386 20130101; H01M 2004/021 20130101; H01M 4/133 20130101;
H01M 4/626 20130101; Y02E 60/10 20130101; H01M 4/134 20130101; H01M
10/052 20130101; H01M 4/366 20130101; H01M 10/0525 20130101; Y02E
60/122 20130101; H01M 4/587 20130101 |
International
Class: |
H01M 4/133 20060101
H01M004/133; H01M 4/38 20060101 H01M004/38; H01M 10/0525 20060101
H01M010/0525; H01M 4/134 20060101 H01M004/134 |
Claims
1. An active material layer for an electrode of a lithium ion
battery comprising: a first active material comprising a
silicon-based particles; a second active material comprising
graphite; and conduits between the first active material and the
second active material, the conduits being conductive and providing
area for expansion of the first active material due to lithiation
while maintaining contact between the first active material and the
second active material.
2. The active material layer of claim 1, wherein the conduits are
carbon nanotubes.
3. The active material layer of claim 2, wherein the carbon
nanotubes are grown on the first active material and in contact
with the second active material.
4. The active material layer of claim 2, wherein the carbon
nanotubes are grown on the second active material and in contact
with the first active material.
5. The active material layer of claim 2, wherein each carbon
nanotube has a first diameter and each silicon-based particle has a
second diameter, the first diameter being larger than the second
diameter.
6. The active material layer of claim 5, wherein the first diameter
is fifty nanometers or greater.
7. The active material layer of claim 2, wherein the carbon
nanotubes have a length of up to thirty microns.
8. The active material layer of claim 1, wherein the conduits are
conductive hollow metal wires of a material that is unreactive with
lithium.
9. The active material layer of claim 8, wherein the conductive
hollow metal wires are inserted into the first active material and
are in contact with the second active material.
10. The active material layer of claim 8, wherein the conductive
hollow metal wires are inserted into the second active material and
are in contact with the first active material.
11. The active material layer of claim 8, wherein the conductive
hollow metal wires have a first diameter and the silicon-based
particles have a second diameter, the first diameter being larger
than the second diameter.
12. The active material layer of claim 11, wherein the first
diameter is fifty nanometers or greater.
13. An anode of a lithium ion battery comprising: a current
collector; a separator; an active material layer between the
current collector and the separator, the active material layer
comprising: a first active material comprising alloying particles;
a second active material comprising a carbon material; and conduits
of a conductive material positioned between the first active
material and the second active material, wherein: during
lithiation, the first active material expands along the conduits
toward the second active material and during delithiation, the
first active material contracts along the conduits, the conduits
providing continuous contact between the first active material and
the second active material during lithiation and delithiation.
14. The anode of claim 13, wherein the alloying particles are one
or more of silicon, tin and germanium.
15. The anode of claim 13, wherein the conduits are carbon
nanotubes.
16. The anode of claim 15, wherein the carbon nanotubes are grown
on the first active material and in contact with the second active
material.
17. The anode of claim 15, wherein the carbon nanotubes are grown
on the second active material and in contact with the first active
material.
18. The anode of claim 15, wherein each carbon nanotube has a first
diameter and each alloying particle has a second diameter, the
first diameter being larger than the second diameter.
19. The anode of claim 18, wherein the first diameter is fifty
nanometers or greater.
20. The anode of claim 15, wherein the carbon nanotubes have a
length of up to thirty microns.
Description
TECHNICAL FIELD
[0001] This disclosure relates to an active material for use in an
electrode having an expansion structures that maintain conductive
contact between active material particles.
BACKGROUND
[0002] Hybrid vehicles (HEV) and electric vehicles (EV) use
chargeable-dischargeable power sources. Secondary batteries such as
lithium-ion batteries are typical power sources for HEV and EV
vehicles. Lithium-ion secondary batteries typically use carbon,
such as graphite, as the anode electrode. Graphite materials are
very stable and exhibit good cycle-life and durability. However,
graphite material suffers from a low theoretical lithium storage
capacity of only about 372 mAh/g. This low storage capacity results
in poor energy density of the lithium-ion battery and low electric
mileage per charge.
[0003] To increase the theoretical lithium storage capacity,
silicon has been added to active materials. However, silicon active
materials suffer from rapid capacity fade, poor cycle life and poor
durability. One primary cause of this rapid capacity fade is the
massive volume expansion of silicon (typically up to 300%) upon
lithium insertion. Volume expansion of silicon causes particle
cracking and pulverization. This deteriorative phenomenon escalates
to the electrode level, leading to electrode delamination, loss of
porosity, electrical isolation of the active material, increase in
electrode thickness, rapid capacity fade and ultimate cell
failure.
SUMMARY
[0004] Disclosed herein are active material layers that provide a
structure for expansion of high capacity alloying particles, the
structure maintaining contact between active material particles
through the life of the electrode. Also disclosed are electrodes
and batteries utilizing the active materials.
[0005] An embodiment of the active material layer for an electrode
of a lithium ion battery has a first active material comprising
silicon-based particles, a second active material comprising
graphite and conduits between the first active material and the
second active material. The conduits are conductive and provide
area for expansion of the first active material due to lithiation
while maintaining contact between the first active material and the
second active material.
[0006] An embodiment of an anode of a lithium ion battery includes
a current collector, a separator and an active material layer
between the current collector and the separator. The active
material layer comprises first active material comprising alloying
particles, second active material comprising a carbon material and
conduits of a conductive material positioned between the first
active material and the second active material. During lithiation,
the first active material expands along the conduit toward the
second active material. During delithiation, the first active
material contracts along the conduit, the conduit providing
continuous contact between the first active material and the second
active material during lithiation and delithiation.
[0007] These and other aspects of the present disclosure are
disclosed in the following detailed description of the embodiments,
the appended claims and the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The invention is best understood from the following detailed
description when read in conjunction with the accompanying
drawings. It is emphasized that, according to common practice, the
various features of the drawings are not to-scale. On the contrary,
the dimensions of the various features are arbitrarily expanded or
reduced for clarity.
[0009] FIG. 1A illustrates an active material layer for an
electrode as disclosed herein, the first active material in a
delithiated state.
[0010] FIG. 1B illustrates the active material layer for an
electrode of FIG. 1A with the first active material in a lithiated
state.
[0011] FIG. 2 illustrates the diameter of the conduit compared to
the diameter of the alloying particle.
[0012] FIG. 3A illustrates another active material layer for an
electrode as disclosed herein, the first active material in a
delithiated state.
[0013] FIG. 3B illustrates the active material layer for an
electrode of FIG. 3A with the first active material in a lithiated
state.
[0014] FIG. 4A is a partial enlarged cross section of the active
material in a delithiated state.
[0015] FIG. 4B is a partial enlarged cross section of the active
material in a lithiated state.
DETAILED DESCRIPTION
[0016] Because the carbon material used in electrodes of
conventional batteries, such as lithium ion batteries or sodium ion
batteries, suffers from a low specific capacity, the conventional
battery has poor energy density even though there is small
polarization and good stability. Furthermore, batteries having
electrodes of graphite or other carbon materials develop increased
internal resistance over time, which decreases their ability to
deliver current.
[0017] To address the poor energy density of carbon based
electrodes, alternative active materials with higher energy
densities are desired. Alloying particles such as silicon, tin,
germanium and their oxides and alloys are non-limiting examples of
materials that may be added to an electrode active material layer
to improve its energy density, among other benefits.
[0018] One particular example is the use of silicon in lithium-ion
batteries. Electrode materials such as silicon react with lithium
via a different mechanism than graphite. Lithium forms alloys with
silicon materials, which involves breaking the bonds between host
atoms, causing dramatic structural changes in the process. Since
the silicon does not constrain the reaction, anode materials that
form alloys can have much higher specific capacity than
intercalation electrode materials such as graphite. Silicon based
anode active materials have potential as a replacement for the
carbon material of conventional lithium-ion battery anodes due to
silicon's high theoretical lithium storage capacity of 3500 to 4400
mAh/g. Such a high theoretical storage capacity could significantly
enhance the energy density of the lithium-ion batteries. However,
silicon active materials suffer from rapid capacity fade, poor
cycle life and poor durability. One primary cause of this rapid
capacity fade is the massive volume expansion of silicon (typically
up to 300%) and structural changes due to lithium insertion. Volume
expansion of silicon can cause particle cracking and pulverization
when the silicon has no room to expand, which leads to delamination
of the active material from the current collector, electrical
isolation of the fractured or pulverized active material, capacity
fade due to collapsed conductive pathways, and increased internal
resistance over time.
[0019] Disclosed herein are active material layers for use in
electrodes and batteries. The active material of the active
material layers include alloying particles that have high capacity
for lithium but undergo large volume expansions due to this high
capacity. The active material further includes carbon material
particles. The active material layers also include conductive
conduits between the alloying material and the carbon material that
provide structure along which the alloying material expands and
contracts, the conductive conduits maintaining contact between the
alloying material and the carbon material during repetitive
expansion and contraction, reducing pulverization and fracturing of
active material particles, and reducing electrical isolation and
internal resistance over the life of the electrode.
[0020] An embodiment of the active material layer 10 for an
electrode of a lithium ion battery is illustrated in FIGS. 1A and
1B. The active material layer 10 is comprised of first active
material 12 comprising alloying particles and second active
material 14 comprising a carbon material. The active material layer
10 further includes conduits 16 between the first active material
12 and the second active material 14. The conduits 16 are a
conductive material and provide area for expansion of the alloying
particles of the first active material 12 due to lithiation while
maintaining contact between the first active material 12 and the
second active material 14. FIGS. 4A and 4B are enlarged cross
sectional views of the first active material 12 in an unexpanded or
delithiated state. As illustrated in FIG. 4A, the conduit 16
maintains conductive contact between the first active material 12
and the second active material 14 when the second active material
14 is delithiated. As illustrated in FIG. 4B, as the first active
material 12 expands due to lithiation, the first active material 12
expands into and around the conduit 16.
[0021] The alloying particles of the first active material 12 can
be silicon-based or tin-based, for example. The silicon-based
particles can be silicon, a silicon alloy, a silicon/germanium
composite, silicon oxide and combinations thereof. The tin-based
particles can be tin, tin oxide, a tin alloy and combinations
thereof. Other high energy density materials known to those skilled
in the art are also contemplated. The second active material 14 can
include one or more of graphene, graphite, surface modified
graphite, carbon nanotubes, carbon black, hard carbon, soft carbon
and any other carbon materials known to those skilled in the art
having the requisite electrochemical activity.
[0022] The ratio of first active material 12 to second active
material 14 can be any ratio known to those skilled in the art to
provide the requisite electrode capacity. The particle sizes of
alloying particles in the first active material 12 and carbon-based
particles in the second active material 14 can also be sizes that
those skilled in the art would use in active material for an
electrode. The sizes can vary within the active material layer 10
or can be uniform within the active material layer 10.
[0023] The conduits 16 are conducting tubes, nanotubes, or hollow
wires that provide a conductive interface between the first active
material 12 and the second active material 14. The conduits 16 can
be a carbon material. An example of a material for use as the
conduits 16 is carbon nanotubes. The carbon nanotubes can be single
or multi-walled and can have any cross-sectional shape as desired
or required. The conduits 16 can also be formed from conductive
metal wires, and in particular, hollow wires, made of a material
that does not react with lithium when used in a lithium based
battery.
[0024] As illustrated in FIG. 2, the diameter of each conduit 16 is
greater than a diameter of each alloying particle 18 in the first
active material 12. The diameter of a conduit 16 can be, for
example, fifty nanometers or greater. Each conduit 16 can have a
length of up to thirty microns. The diameter and length of each
conduit 16 can be uniform throughout the active material layer 10
or can vary throughout the active material layer 10.
[0025] The conduits 16 can be grown on or inserted into the first
active material 12 as illustrated in FIGS. 1A and 1B. One example
of growing carbon nanotubes on a silicon-based active material
comprises mixing the carbon nanotubes with silicon gel such as
tetraethyl orthosilicate gel or silicon dioxide gel to form a
homogenous gel. The mixture is then spray dried and calcined in a
furnace under a reducing atmosphere at about 1000.degree. C. to
about 1300.degree. C. to form spheres of the active material with
conduit grown on the spheres.
[0026] Alternatively, the conduits 16 can be grown or inserted into
the second active material 1 as illustrated in FIGS. 3A and 3B.
[0027] Also disclosed is an anode of a lithium-ion battery
incorporating the active material layers 10 disclosed herein. The
power generating element of the lithium-ion battery includes a
plurality of unit cell layers each including a cathode active
material layer, an electrolyte layer and the anode active material
layer 10 disclosed herein. The cathode active material layer is
formed on one surface of a current collector and electrically
connected thereto and the anode active material layer 10 is formed
on the other surface of the current collector and electrically
connected thereto. Each of the electrolyte layers includes a
separator serving as a substrate and an electrolyte supported by
the separator.
[0028] Examples of the cathode active material layer may include
lithium-transition metal composite oxides such as
LiMn.sub.2O.sub.4, LiCoO.sub.2, LiNiO.sub.2, Li(Ni--Co--Mn)O.sub.2,
lithium-transition metal phosphate compounds, and
lithium-transition metal sulfate compounds. These are provided by
means of example and are not meant to be limiting. As the
electrolyte constituting the electrolyte layer, a liquid
electrolyte, a gel electrolyte or a polymer electrolyte known to
those skilled in the art may be used. As examples, the liquid
electrolyte may be in the form of a solution in which a lithium
salt is dissolved in an organic solvent. The gel electrolyte may be
in the form of a gel in which the above mentioned liquid
electrolyte is impregnated into a matrix polymer composed of an ion
conductive polymer. When the electrolyte layers are formed by a
liquid electrolyte or gel electrolyte, a separator may be used in
the electrolyte layer. Examples of the separators are porous films
of polyolefin such as polyethylene and polypropylene. The current
collector is composed of a conductive material serving as a joining
member for electrically connecting the active material layers to
the outside.
[0029] As described herein, the methods and systems include a
series of steps. Unless otherwise indicated, the steps described
may be processed in different orders, including in parallel.
Moreover, steps other than those described may be included in
certain implementations, or described steps may be omitted or
combined, and not depart from the teachings herein. The use of the
term "collecting" is not meant to be limiting and encompasses both
actively collecting and receiving data.
[0030] The words "example" or "exemplary" are used herein to mean
serving as an example, instance, or illustration. Any aspect or
design described herein as "example" or "exemplary" is not
necessarily to be construed as preferred or advantageous over other
aspects or designs. Rather, use of the words "example" or
"exemplary" is intended to present concepts in a concrete fashion.
As used in this application, the term "or" is intended to mean an
inclusive "or" rather than an exclusive "or". That is, unless
specified otherwise, or clear from context, "X includes A or B" is
intended to mean any of the natural inclusive permutations. That
is, if X includes A or B, X can include A alone, X can include B
alone or X can include both A and B. In addition, the articles "a"
and "an" as used in this application and the appended claims should
generally be construed to mean "one or more" unless specified
otherwise or clear from context to be directed to a singular
form.
[0031] The above-described embodiments, implementations and aspects
have been described in order to allow easy understanding of the
present invention and do not limit the present invention. On the
contrary, the invention is intended to cover various modifications
and equivalent arrangements included within the scope of the
appended claims, which scope is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structure as is permitted under the law.
[0032] Other embodiments or implementations may be within the scope
of the following claims.
* * * * *